Copyright © Michael Richmond.
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Argon gas contains molecules, each of which is a single argon atom. The mass of a argon atom is 40 atomic mass units.
Question 1: What is the mass of 1 mole of argon gas?
Answer: mass (grams) = mass of molecule (atomic mass units)
= 40 g
Joe places 8 grams of argon gas into a balloon.
Question 2: How many moles of argon are in the balloon?
Answer: # moles = (mass of sample)/(mass of 1 mole)
= (8 g)/(40 g) = 0.2 moles
Question 3: How many molecules of argon are in the balloon?
Answer: # molecules = (# of moles)*(Avagadro's number)
= (0.2) * (6.022 x 10^23) = 1.20 x 10^23
The balloon inflates to a diameter of 12 cm.
Question 4: What is the volume of the balloon, in cubic meters?
Answer: 4*pi
volume = ----- (radius)^3
3
4*pi*(0.06 m)^3
= --------------- = 9.05 x 10^(-4) m^3
3
The gas inside the balloon has a temperature of 15 degrees Celsius.
Question 5: What is the pressure of the gas inside the balloon?
Answer: PV = nRT
Note that temperature must be expressed in Kelvin:
T(kelvin) = T(celsius) + 273 = 288 K
Solve for pressure P:
nRT (0.2 moles)*(8.31 J/mol*K)*(288 K)
P = ------- = ----------------------------------
V 9.05 x 10^(-4) m^3
= 5.29 x 10^5 N/m^2 = 5.29 x 10^5 Pa
This page maintained by Michael Richmond. Last modified Jan 16, 1997.
Copyright © Michael Richmond.
This work is licensed under a Creative Commons License.